The present invention pertains to an apparatus for and a method of uniform treatment of fluid volumes using external irradiation sources. More particularly, the present invention pertains to an apparatus for and a method of treating a volume of fluid in a fluid passageway by irradiating the fluid passageway from an external irradiation source to provide a substantially uniform irradiation distribution within the fluid in the fluid passageway.
During the irradiation treatment of fluids flowing through fluid passageways, the uniformity of irradiation is of primary importance. By way of example, the fluid might be treated with ultraviolet irradiation so as to disinfect, purify, or cause oxidation of material within the fluid. If the irradiation is not uniform, those portions of the fluid flowing through the regions of low irradiation intensity may be undertreated, while portions in the vicinity of peak irradiation fields may receive higher than desired doses of irradiation which could damage material within the fluid. This problem is even more significant in the case of turbid fluids or fluids of high absorptivity for the applied irradiation.
Known techniques for irradiation of volumes of fluid include immersing multiple irradiation sources in the fluid. However, this is complex and costly, requiring multiple irradiation sources and introducing additional problems of cumulative absorption caused by impurities on the irradiation source-fluid interface. Cleaning mechanisms and processes have been proposed to overcome this last problem, but these are likewise elaborate and complex. Potential irradiation source accidents introduce additional risks of pollution of the fluid and the distribution system by the hazardous irradiation source components.
A second approach is to restrict the fluid flow, avoiding underexposed volumes. This scheme suffers from limited efficiency, high pressure drops, and high cost of pumps necessary to achieve the desired flow.
Another approach is to introduce mixing devices in the fluid flow, in the hope that each portion of the fluid will receive an xe2x80x9caveragexe2x80x9d treatment. This approach likewise suffers from efficiency problems, as well as the more serious problems of likely undertreatment of a portion of the fluid volume.
A further approach is to present the fluid as a thin film to the irradiation. This approach does not take into account the absorption of the source, the fluid passageway, and the fluid itself, nor the indices of refraction of the fluid passageway material or the fluid, and hence the real energy distribution in the thin film of fluid.
The present invention is an apparatus for and a method of uniformly treating fluid volumes. In accordance with the present invention a fluid passageway is provided, through which the fluid flows. At least one source of irradiation, external to the fluid passageway, produces irradiation to irradiate the fluid flowing within the fluid passageway. The apparatus further includes at least two elongated elliptical reflecting troughs for reflecting light from the at least one source of irradiation onto the fluid flowing within the fluid passageway. The troughs have openings facing each other to define a space between the closed elliptical ends of the troughs. The ellipse of each trough has a first focal point within the trough, the locus of which over the length of the troughs defines a first focal axis. Further, the ellipse of each trough has a second focal point outside the trough, the locus of which defines a second focal axis. The fluid passageway and each source of irradiation are positioned in the space. At least one of the fluid passageway and the at least one source of irradiation is spaced from the focal axes of the troughs so that the irradiation irradiating the fluid passageway is defocused. As a consequence, the fluid in the passageway is irradiated with a substantially uniform irradiation distribution, even in a fluid passageway of relatively large internal diameter.